FAQ

Technical Information

FAQ (Frequently Asked Questions)

Why am I seeing lots of aliased noise in my data?

Does your acquisition system setup include one of our power supply or data acquisition units? If not make sure you have applied a suitable low pass filter in your setup to deal with the excitation frequency of the sensor. You can either apply an analogue low pass filter, or digitise the signal at a frequency at least twice that of the excitation frequency. Please refer to your sensor’s brochure for details on excitation frequency and breakthrough levels.

Is the magnetometer output signal conditioned?

The output from the magnetometer is an analogue voltage which can be connected to the customers own appropriate data acquisition system(DAQ). It should be noted that there is some residual breakthrough from the sensors excitation which is partially filtered inside the sensor (by an analogue low-pass filter). This is then further filtered out by our power supplies and DAQs. If using own acquisition system, you would need to filter this out either by fitting an analogue low pass filter or by digitally sampling at least double the excitation frequency of the sensor. Alternatively, we could provide a PSU1 which would deliver power to the sensor and filter the output so that you can then connect it to your own DAQ without the need for additional filtering.

Can I measure the absolute magnetic field accurately or only variations in magnetic field?

In order to achieve absolute measurements, scaling, orthogonality and offsets errors will need to be corrected. Multiple papers discuss the calibration of fluxgate magnetometers for use in total field measurements with varying level of success. One example is:

Munschy et al., 2007. Magnetic mapping for the detection and characterization of UXO: Use of multi-sensor fluxgate 3-axis magnetometers and methods of interpretation: Journal of Applied Geophysics, 61.

How does scaling error effect measurements?

The scaling error is the difference between the applied field and the measured field. The scaling parameter will be stable over time, but is affected slightly by temperature changes. The scaling error is a stable value and, as such, a multiplying factor can be applied to the sensor readings to correct for it. Regular calibration will allow you to get the most up to date parameters for your sensor.

How does the orthogonality error effect my measurement?

The orthogonality error is a constant error. It is due to the three axes not being exactly 90 degrees from each other. A correctional matrix can be applied to get the readings that would be expected if the axes were perfectly orthogonal to each other.

What is the measuring range of a sensor?

The range is included at the end of the sensor name. For example, a Mag-03MC70 is a Mag-03 with measuring range of 70µT. The range is also printed on the sensor’s label.

How do I know which noise version my sensor is?

The noise is indicated by the letter found after the product/package reference. Q for very low noise (Mag-13 only), L is for low noise, no letter will indicate a standard noise and B a basic noise. Refer to the product datasheet for the noise levels. For example, Mag-13MCQ is an cylindrical package Mag-13 with noise level below 5pTrms/√Hz @ 1Hz.

Where are the fluxgate sensors located?

Where possible, the fluxgate sensors are located in the centre axis of the sensor below the axes marking on the sensor. However, this is for indication only (and not always feasible to position the label right above the axes). For exact position, refer to the sensor’s outline drawing available on the product page at www.bartington.com.

Which is the sensor’s mounting face?

Refer to the sensor’s outline drawing available on the product page at bartington.com as the mounting face change from sensor to sensor.

What is the breakthrough?

This is the amount of signal at the excitation frequency of the sensor present on the sensor’s output – please refer to glossary

Can I use a sensor in vacuum?

Some sensors are designed for operation in vacuum (Mag-03IEHV for example – tested to pressure of 1e-4 Pa). Customers have in the past used non-tested sensors in low pressure environment, but we do not guarantee that the sensor will not be subjected to damage or severely outgas.

Can I use the sensor at low/high temperature?

Only the Mag F and G probe are rated for cryogenic use. Sensors with integrated electronics will not operate at low temperature whilst other two parts sensors will suffer mechanical damage at low temperature (wire insulation breaking etc…). For high temperature use, only the Mag610/611 and Mag614 have been tested to operation above 175°C. This is the probe only – please refer to the individual brochure for specific operating temperatures.

Can I subject the sensor to shock and vibrations?

Only a few of our aerospace and high temperature downhole sensors have been formally subjected to shock and vibrations tests (where applicable the test method is provided in the product datasheet). Other sensors have been used in those environment successfully over the years (for example Mag-03 are regularly mounted onto aircraft).

How far from the electronics can I position the sensor head in a two part sensor?

Most two part sensors have a maximum separation of ~5m. This depends on the sensor being used, to refer to the product datasheet for details.

How close together can I place two sensors?

If one sensor is active and the second one off, the sensors should be kept about 4-5cm apart (sensor dependent as the dimensions of the core material vary). The interference between two sensors as described above is a small DC offset on the active sensor. When the two sensors are powered (unless you are using multiple Mag612 or Mag619 with the excitation synchronised), the minimum distance should be between 15-20mm. A beating phenomenon may otherwise occur where one sensor is picking up the excitation from the other. As it is unlikely that the excitation will be at the same frequency and in phase, a beating (low frequency signal) appears on the output of the sensors.

Are flying leads/cable connecting sensor to electronics shielded?

No, these are not shielded, and can therefore be the source of noise pick-up in the system. It is therefore essential to shield these to prevent any issues.

What signal does the voltage output from the magnetometer/PSU1 represent?

The output voltage of ±10V or ±3V (full scale output dependent on sensor, please refer to individual brochures) represents the full scale range of your sensor. For example, if you have a ±100µT range sensor on a ±10V full scale output the scaling will be 100mV/µT. This voltage gives both the DC and AC components of the field.

What is the resolution of a magnetometer?

As the sensors have an analogue voltage output, there is no defined resolution. Instead, the smallest fields detectable by a sensor are dependent mainly on the sensitivity of the voltmeter being used to read the output voltage, the internal noise of the sensor, and environmental noise. The internal noise of the sensor is the absolute minimum that the sensor can detect. However, the magnetic noise in the environment is higher than this, and will limit the smallest variation that can be detected. If data processing is performed, the environmental noise can be removed and the sensor noise level can be reached. The scaling (sensitivity of voltmeter) of the analogue output varies with the range of the sensor. Scaling values for different sensors are listed in the sensor’s datasheet. The scaling value increases as the range of the sensor decreases, increasing the sensitivity as the range is reduced.

When should a sensor be calibrated?

We recommend that sensors are calibrated every two years months. Sensors must be returned to Bartington Instruments for calibration.

Can I mount a Mag-03MC to a surveyor's tripod, using the wooden bracket and nylon screws?

We are unaware of anyone who has a design that you can use. However, Bartington manufactures the Mag-03-MC Mounting Bracket DR0746(2) for similar applications. For a drawing of the bracket, see figure 17 in the Mag-03 Operation Manual. This product could be adapted for your application.

It is very important to ensure that there is no steel in the tripod. We supply an aluminium tripod for mounting the Mag03MC, the Mag-03-T (Tripod). This extends to 1.3 metres, and comes with a tripod adaptor for mounting the Mag-03MC. Contact us at sales@bartington.com for further details.

What happens if I apply AC or DC field over the range of my sensor?

If it is saturated by an AC field, then it is not too much of an issue. If you can reduce the amplitude of the field progressively to come out of saturation (similar to what would be done during deperming) or stop the AC field when it is close to 0. If it is saturated at DC, or you switch off abruptly an AC field at high amplitude, then refer to the overload hysteresis figure in the brochure. Typically an offset will be added, the more important the offset for the higher the over-range.

Is the sensor's output affected by the voltage supply?

There is always some overshoot above the full-scale output. Typically, the output of the sensor is driven by the op-amp on the electronics which will have an output function of the voltage supply. If you supply 12V, for instance, you may have a maximum output which will be around 10.5V. As you increase the voltage supply you can gain a few hundred mV on the output (we no longer guarantee that the output will be linear). So if you end up with field above 110-120uT, the output will reach the rail (which will be slightly above 10V) and stay there until the field comes back within sensor range.

How long can the cable to my sensor be?

We can drive sensors with cables up to a several hundred metres, but this depends on the sensor being used. Contact sales@bartington.com for more about using cables over 30 metres long.

The CU1 is emitting a loud continuous noise

This noise indicates that the connection between the CU1 and the National Instruments (NI)/PC/Software has not been detected. To troubleshoot this please shut everything down, then try restarting everything in the following order: your PC + Software, then NI card, then CU1 and finally the PA1.

No power is being provided to the sensor plugged into the DUT port of the CU1

Make sure to check that the DUT PSU is enabled in the software and that a suitable voltage has been set (refer to sensor datasheet for the correct voltage range).

I am applying a known DC field and I am not reading the correct value in the measurements tab in the software.

Please check in the software settings that the measurements are set to DC and not RMS or pk-pk in the measure tab.

I am applying a known AC field and I am not reading the correct values in the measurements tab in the software?

Please check in the software settings that the measurements are set to either RMS or pk-pk in the measure tab.

The amplitude of field being generated is not reaching the value I’ve set in the software and I’ve made sure that the measurement type is correctly set for the type of signal I am generating (ie. DC for DC or RMS or Pk-pk for AC)

Please check that the field you are trying to generate does not overreach the limitations of the coil/PA1 combination being used. For example you haven’t overreached the maximum of 20A per coil or the overall maximum of 29A for all coils and PA1. Please also check that the frequency is not too high for AC fields. There is a maximum limit of 5 kHz and the higher the frequency of the generated field the lower the maximum field you will be able to generate, based on the maximum of 20A current through the coils/votage available to deliver that current.

The measured amplitude on one axis is not as expected

Ensure that the sensor is aligned to the coils. Any misalignment will lead to the signals present on the X Y and Z axes to be lower than those applied by the coils.

What is the recommended time period for measurements?

It depends on how stable the sample and the temperature are. In the lab, where MS2B an MS2C are most likely to be used and conditions are more stable, 5 sec measurement period is fine whereas in the field where MS2E and MS2K are used, 1 sec measurement is recommended.

Is the MS2 range limited by the 4 digit display?

Indeed, there is a limitation to 4 digits on the display, however, there is a workaround available for samples above this range. (described for MS2B but will also work for other sensors, where the sample is brought closer to the sensor slowly). Place the sample on the platen and lower it slowly within the sample cavity while continuously monitoring the display readings. You will notice that as you lower the sample the susceptibility value increases up to 9999 and then switches back to 0000. That practically means that your sample has a value over 10000 of which the first digit is omitted so you only see 0000. Keep lowering the sample until you reach the centre point and note how many time your values resets to 0000. i.e. for a value of 35000 the display will reach 9999 three times during lowering and display 5000 once the platen has been fully lowered to the centre point.

Is BartsoftPC compatible with windows 8?

We are pleased to advise that it is, although not with Windows 8 RT (for mobile devices which is built upon ARM architecture). This is a limitation imposed by the Windows 8 RT architecture and not the Bartsoft for PC software.

Is the MS2C sensor waterproof?

The MS2C sensor does not have an IP marking as such, however, it does contain an internal seal which protects the internal electronics from water ingress as well as wax and silicon sealant around the screws. This would be suitable for protection from splashes of water but not for submersion. Note that the connector on the back of MS2C does not have any protection and should be kept dry at all times.

Can I measure irregularly shaped rock samples with my MS2B?

It should be possible to obtain magnetic susceptibility measurements for your irregularly shaped rock samples. Ideally these samples would fit within the 10ml pots provided. This will make sure that all of the sample is within the area of response of the coil. You will then need to calculate the volume of your sample in ml, one way could be by measuring the displacement of water from the pot when the sample is added. A correction is then available in the Bartsoft software if you select the ‘Individual Sample Study’ – MS2B report type and the ‘Volume Specific Correction’ in the ‘Correction Selection’ menu. If you enter the volume of your sample in ml the correction will account for the missing volume of the pot which is filled with air. It is also possible to apply a mass specific correction if the mass (g) and volume (ml) are both known. For the mass specific correction the mass of the empty pot should also be subtracted to give the mass of the sample only. If possible the samples should fill more than 50% of the sample pot, this is because once the sample volumes become very small the irregular shape can begin to impact the measurement.

Can I use your AC susceptibility instruments to measure stainless steel?

Please see application note 17 which describes the use of our MS2K sensor for measuring stainless steel. It mentions the potential pitfalls of the AC susceptibility method, this being that high sample conductivity can give rise to a negative susceptibility reading due to interference from induced magnetic fields. The application note refers to some successful measurements that were performed on stainless steels with approximate resistivities described.

We are struggling to obtain GPS readings with our susceptibility measurements using Bartsoft on the Trimble Nomad, i.e. Bartsoft is not recognising the GPS, and can you help?

When connecting the MS3 to the Trimble handset, it is important to ensure that the Trimble is powered up before connecting the MS3. Secondly the GPS management program needs to be started and a connection with the satellites established prior to starting the Bartsoft software. In addition to the above please ensure you are running the latest version of both software.

Do you have any available documentation or code available to help me directly access and control my MS3 measurements using third party software such as LabView or Matlab?

We do not currently have suitable libraries available for interfacing the MS3 to Matlab or Labview. However, we can provide a document listing the MS3 USB communications protocols. Perhaps this information will be helpful and enable you to generate a solution. An alternative suggestions might be to use the RS232 connection rather than USB. For the RS232 communications an MM command can be sent to trigger continuous measurement, ZZ for zero measurement and any other key to interrupt and stop measurements.

I see quite a strong sensitivity to temperature with my MS2E when measuring cold sediment soil cores?

As the MS2E sensor requires contact with a sample for successful measurement as well as the fact that the coil housing is ceramic (good conductor of heat) this sensor can be very sensitive to temperature drift. We advise acclimatising the sensor to the temperature of your samples before measuring. For example if cold cores are being measured a suggestion might be to carry out your measurements in the cold fridge. Alternatively, bring everything to room temperature before making measurements.

We are struggling with set up of our MS3 Susceptibility/Temperature system, can you provide any troubleshooting advice?

Have you connected the MS3 to the MS2WFP, and then the MS2WFP to the PC? Have you first set the RS232 communication mode of the MS3 to mode B by connecting it initially with the USB cable and checking the settings in Bartsoft? Are you connecting via a USB to serial cable, and are the drivers up to date? Are the serial port settings correct?

I have just acquired an MS3. I am looking for a small device (phone or tablet) for using it on the field. What can you suggest?

The device that we recommend and can provide is the Trimble Nomad 900L field computer. The MS3 has also been successfully tested using an Archer 2. The key features required by a PDA to be used with an MS3 are that it runs Windows Mobile 5 or 6, and that it has a USB port that can power an external device. Or see the new system provided by Terrasurveyor.

Is it possible to use and MS3 meter with the susceptibility/temperature system instead of the MS2 meter?

It is possible to use the MS3 meter with the Temperature/Susceptibility system by use of the RS232 connector and 5V power supply. You will also need to ensure the MS3 is set to communications mode B by installing Bartsoft, plugging in the MS3 with the USB cable, opening the Meter window, clicking on ‘RS232 Setting’ and selecting mode B. The MS3 can then be plugged into the MS2WFP via the RS232 cable and used with the Geolab software.

Can I use the MS3 with the Multisus software?

The Mutisus software can only be used with the MS2 via RS232 connection. It is now recommended to use the Bartsoft Software as this is compatible with both MS2 and MS3 devices via serial or USB connection and has increased functionality over Multisus.

Is the Multisus/Bartsoft software compatible with Mac devices?

Currently our software and device drivers are only compatible with Windows operating systems.

How do I properly test the calibration sample supplied with the MS2E/MS2K sensor?

Some users of the MS2E or MS2K sensor may be unsure which face of the calibration sample (provided with the sensor) should be used during its calibration. It is the black coloured bottom of the red plastic sample container that must be measured, and not its top where the calibration label is located. It is also important that the black lines, either side of the calibration label, should be orientated with the marks on the MS2E sensor head that indicate its long axis. The measurement obtained should be within 5% of the value printed on the sample calibration label.

When using BartsoftPC I import a .bid file and export it but the exported file has only the column headers and no data, please can you assist?

With this type of problem, the first thing to check is that you are running the latest version of Bartsoft PC software. This can be downloaded from the Bartington Instruments website :http://www.bartington.com/software.html.

When taking a reading of my calibration sample it seems to have drifted by a couple of orders of magnitude, do you have any troubleshooting advice?

The calibration sample can be incorrectly aligned with the sensor head whilst making the measurement. Make sure the markers line up with the sensing area and that you measure from the black underside of the calibration sample. The sensor should be positioned away from any metalwork whilst taking the reading. If holding the calibration sample by hand, no metal watches, bracelets, rings, etc. should be worn. The calibration reading is generally within 2 or 3 % of the value recorded on the top of the calibration sample container and is designed to check the calibration of the sensor. If your reading is still a long way out, then the sensor and meter will have to be returned to us for re-calibration as it is not possible to re-calibrate the sensor using Bartsoft.

Why am I getting run time errors with my MS2/MS2E system?

Run time errors occur when a file has become corrupted during the install. The best solution is to uninstall and remove the software from your machine, then download a fresh version from our website’s software page and re-install the program. This should remove your problem.

I am a new user of Bartington MS3, could you please give me the details about how to set the "Measuring protocol" if I want to use the MS3 Magnetic Susceptibility Meter and MS2D to measure the regional soils magnetic susceptibility in-situ?

Using Bartsoft, the measuring protocol for the MS2D sensor should include 1x blank measurement at the start, followed by infinity x sample measurement (for as many in situ samples as required) and a final 1x blank measurement at the end. The 2 blank measurements are to calculate any drift and remove it from your sample readings. The blank measurements should be taken by lifting the sensor up in the air to ensure nothing is within the sensing range, it is also possible to alter the length of each measurement using the drop down menus in the measuring protocol window. If you wish to record the measurement positions within a grid, tick the automatic grid position inputs box and enter the size of the grid and measurement intervals in the position assignation window.

Bartsoft does not recognise my MS3 device what could be the problem, can you offer any troubleshooting advice (PC Version)?

While an MS3 device is connected to the host PC, open the Device Manager and check that both drivers (Expand Jungo, 1-Bartington Instruments, 2-Magnetic Susceptibility Device) do exist and are working properly. If they seem to be working, check the hardware, including the MS3’s USB cable. Also ensure that the host PC’s USB port is functioning correctly (e.g. when other devices are connected). If the device drivers are not working correctly, this may occur if the latest versions of the drivers are not present. Uninstall the application and when prompted, ensure the device driver is also uninstalled. Make sure that the MS3 device is disconnected, before attempting to uninstall the driver. After the uninstall is complete, restart the PC and download the latest version of the software from www.bartington.com/software and install it, making sure to select the 32 or 64bit version as appropriate. On completion of the installation, restart the PC for the second time and then connect the MS3 device, before waiting for a few seconds for the Operating System to load the driver of the device.

When using serial communication with either MS2 or MS3 the software does not receive any data?

Double check that the correct com port has been selected in Bartsoft or Multisus (look in the device manager for the correct com port to use) and also ensure that the baud rate and number of bits are properly selected for the meter being used. If this setup is all correct one last thing to check is to ensure that the buffer size is dropped to the minimum value.

The LED on my MS3 is orange despite the sensor being connected through USB to my PC?

The orange LED indicates a connection problem between the sensor and the MS3 meter. Check the tnc cable for obvious damage and if you have a second cable try this. If the problem persists, try the MS3 meter with another sensor to rule out an MS3 problem. If the problem persists both sensors and MS3 meter will have to be returned to Bartington for repair.

The LED on my MS3 is red despite the sensor being connected through USB to my PC?

Please make sure that the drivers are all properly installed and up to date, see the operation manual for more information on relevant drivers. If the drivers are all up to date then test the connection using the serial cable. If that works, then likely issue is with USB cable, if it still does not work the MS3 will need to be returned to Bartington for repair.

The LED on my MS3 will not light up, please can you offer some troubleshooting advice?

If the MS3 is being powered through a USB or serial connection the problem is most likely caused by a broken cable or a blown fuse. Please double check that you have not accidentally connected a 12V mains charger into the 5V mains input of the serial cable. If the LED does not come on when using the USB connection, double check this against the serial cable (ensuring to use the 5V charger supplied). If the LED comes on with serial cable, then the problem lies with the USB cable. If you try the serial cable and the LED still does not come on then the most likely problem is a blown fuse and the unit will have to be returned to Bartington for repair.

Can I used the MS2H and the BSS-02B Susceptibility Sondes in larger diameter holes?

The probes are calibrated to measure a full response in a specific diameter hole. As the hole diameter increases the response will drop off. As the diameter of the hole increases the area of response will contain more and more borehole fluid and reduced formation. If the probe is positioned along the side of the borehole wall (decentralized) you will obtain a response from the formation. With a larger hole and the probe decentralized you will be able to measure changes in susceptibility with depth although an absolute susceptibility value may be difficult to achieve without complex borehole corrections. In addition the probe will need to be used in an un-cased borehole (or plastic casing). The presence of metal casing will affect the reading (conductivity creating induced fields which cause interference) and give apparent negative values.

Is your BSS-02B sonde a complete measurement system?

No, the probe needs to be integrated with a customer’s downhole system as we do not provide the surface acquisition equipment. If the customer is interest in a complete downhole system which already has our tool integrated within then we would suggest contacting either downhole logging equipment suppliers. Please contact sales@bartington.com for details.

The Grad-601 works for other people but not for me. A Coarse error appears during setup of the equipment?

It is important that the user is magnetically clean. Make sure to remove all metallic items from your person: watches, mobile phones, jewellery etc. The steel underwire in bras and parts of shoes will also contribute and are often forgotten. Those with metallic implants such as plates, pins or pacemakers may be unable to use the equipment. To test your magnetic cleanliness set the gradiometer to the 100nT range with the appropriate setting for the number of sensors and run in Scan mode. Hold the gradiometer stationary and check the readings when the operator approaches the gradiometer sensor. The operator should check all parts against the end of a gradiometer sensor until a change of less than 0.1nT is seen.

Is it possible to orientate grids to exactly North if a rotation angle is known for the survey area?

It is possible to orientate your grids to different directions. Using the main menu on your datalogger select Set parameters and press ENTER. The third item on the list is Start, this is the starting direction of your survey, step through the options and select the direction you wish to start in. It allows for rotation in 45 degree increments. With a different starting direction, you can orientate your grids accordingly. I hope this offers you the adaptability you were looking for.

Can the Grad601 be used with GPS data?

The current way to use the Grad601 alongside GPS is by having the firmware in the data logger adapted to provide an NMEA output. With this set up the data is streamed to an external logger which is also connected to a GPS device, the logger would contain software capable of logging both GPS and Grad601 data. This method is usually used for cart based systems.

When downloading my data to a computer I get NaN values throughout my survey?

You may be using the wrong version of the download software. When turning on the data logger your firmware version will be displayed on screen. Make sure you have the appropriate download software for your firmware version. For versions 6.3 and before you will need to download software version 313. For version 6.6 and above you should use software version 316.

What is the minimum horizontal sensor separation possible?

The minimum separation between gradiometer sensors is 3cm; however it is likely that some interference may be picked up if the gap between them is less than 10cm.

Can I use the Grad-601 in the rain?

Yes, the Grad-601 is waterproof and can be used in the rain, however it is recommended to put a plastic bag over the data logger to limit its exposure to water. The seals around the sensor connectors should also be checked for cracks or holes and repaired using silicon sealant if required.

I am using a Grad601-2 Dual Gradiometer but the sensors are quite old and there is no heading arrow. Instead there are crosshairs & circles on each sensor. Can you please confirm which direction is the heading – i.e. should the crosshairs be facing outward (i.e. in the direction of survey)?

The cross hair and circle represents an arrow with the cross hairs being the flights. The circle should be pointed in the survey direction as if it were the point of the arrow, with the cross hairs orientated toward the user.

Can you please explain how the range works on the gradiometer, does it measure the absolute field?

The ranges are not a measure of the absolute value of the magnetic field, in fact they represent the difference between the background field and the field measured closer to the ground (the gradient). The +/-100nT range has a better resolution (0.03nT) so it is best to take your survey in this range if possible. If the values are over-ranging because your location has a strong magnetic signature variation, then you also have the possibility of using the +/-1000nT range (0.1nT resolution).

I am seeing a larger than normal gradient drift on my sensor, what should I do?

This could be caused by a number of issues, regardless the sensor will need to be returned for assessment and repair. One possible reason observed previously is that if the paint on the sensor tube is scraped off at the top or bottom this can cause a temperature imbalance between the top and bottom fluxgates, which will show as gradient drift. Some older sensors used internal insulation around the fluxgates and if this starts to come loose a similar temperature imbalance between top and bottom fluxgates may appear.

Can I remove the battery from my battery cassette for replacing?

Yes first remove the 12 screws that hold down the top cover of the battery cassette and lift the cover off. This will then reveal the battery and the associated circuitry. The inside of the cover has a rubber gasket (material sealing the junction between two surfaces) that ensures a tight seal within the cassette. Prise it off from one corner to break the seal and enable the cover to be removed. The battery is not secure and can simply be removed, some have a pull tab attached to assist. The circuitry is part of the cassette and should not be removed. The new battery can then be inserted and the battery cassette put back together and closed with the 12 screws.

What are the main points to consider for successful grad601 data acquisition?

Magnetic cleanliness of the user. Find an appropriate magnetic spot for instrument set up, an area 1-2m square where, when always facing in the same direction, you do not get more than 0.5nT variations. Know where north is as this is required for instrument setup, but be sure to remove any compass from the area when carrying out the setup or surveying as this may cause magnetic interference. Walk at a constant speed when surveying, this can be improved by using visual markers along traverses every meter, there is also an audio signal on the instrument that makes a sound every meter when doing grid acquisition. Keep the instrument position as stable as possible when carrying out measurements.

Can you give a rough idea of the time taken to survey a grid using a grad601-2 system, for example a 30x30m grid?

This really depends on the number of people available and the spacing between traverses (lines). The longest part of the survey is generally the laying out of the grid. It will take roughly 15 minutes to walk a 30m grid at 1 line/meter spacing with a dual system. If acquiring 2 lines/meter you can expect it to take twice as long. This timing is considering the traverses are all laid out or there are two people available to move the trapeze appropriately during acquisition.

Please could you give me a rough idea of the components included in a cart system for the Grad-01-1000L sensors?

The system comprises of the following:

A light and robust carbon fibre cart which can either be hand operated or towed behind a vehicle (using tow attachment). When completely taken apart it takes about 20 minutes to re-assemble the cart, however if transporting in a van, sections can be left together to improve re-assembly time.

The Grad-01-1000L sensors, high precision gradiometer sensors which have proved their quality over the years.

The DL601 data logger, which will digitise the data and transfer them to a laptop. The laptop will be running data logging software which will log all data including GPS co-ordinates. Existing datalogger can be updated to newer electronics boards enabling them to operate in both grid and NMEA modes.

The BC601 battery cassette which can provide power to up to 3 data loggers at once (although usually 2).

A serial to USB hub which enables the connection of the data loggers to a laptop – this is included in the price of the acquisition/logging software.

Logging software for joint collection of Magnetometer and GPS data (run on a standard laptop)

A compatible GPS antenna with NMEA output format.

I am having trouble with a loose connection when charging between battery unit and data logger?

In the past we have seen that the tip of the of the mains adaptor can become loose over time. It may be worth checking this with another adaptor if available, or else we can provide a new charger.

My sensor is measuring a constant 0 gradient, what could this be?

This could be linked to the cable between the datalogger and the Grad sensor, it would be worth inspecting the cable to see if it looks damaged, one way to exclude the cable as the fault will be to swap the sensors round, if connected to the other cable the sensor is still not working then it is a sensor issue.

Why am I getting a course error on my unit when setting up, I know my sensor is working correctly?

The coarse error indicates that the unit was not able to perform the setup procedure correctly – to go a bit more in depth on the sensor application, the sensor has a set of digital potentiometers for which the values are adjusted under the direction of the datalogger. When setup is performed, the data logger tests incremental values on the potentiometers with the overall aim of getting the initial gradient values close to zero in all subsequent N, S, E, W and inverted positions. Two things that often cause the setup to fail with a coarse error: the gradient values are so large that they are saturating the sensors, therefore even when incrementing all the steps of the potentiometer (to its max settings) it cannot bring the values back to within the reading range (100 or 1000nT depending on the settings). The variability in background reading is too high (you have not found a quiet area) so the unit cannot fix on a zero.

What’s the setup procedure?

As a general rule of thumb, in order to acquire good data which will not appear stripy when doing zig-zag surveys, you should find a site, for the setup, for which you do not see variations of more than 0.5nT to 1nT when moving over a 1m squared area (you will need to move in such a way as that the sensor is always pointing in the same direction). When doing the setup make sure that the centre of the instrument is used as the rotation axis rather than yourself – i.e the sensor is always located above the same point.

Are there some tests I can perform before returning my instrument to identify whether it is a sensor/logger/cable error? This will prevent me having to return the full set of equipment?

There are a couple of short tests that it would be worth carrying out, just as a double check to try and isolate the issue before returning the sensor to us:

If you have a dual system you can swap the sensors around and check whether the problem follows the sensor, if it does this suggests a sensor error and we can arrange for its return.

If the problem doesn’t follow the sensor it might suggest a problem with the logger or cable. If you then swap the cables round (by detaching and swapping where they attach to the logger) and check whether the problem follows the cable? If it follows the cable it suggests a cable error, if not it suggests a logger error.

Another test to try is to carry out the setup procedure on each sensor individually (one at a time, in a single grad configuration) and see if this makes any difference.

The screws in my sensors have become magnetised over time, what could the reason be as I am not aware of any exposure to large fields?

On older sensor we have seen a direct link between screws that have become magnetised, these appear to be machined screws, rather than cast. Although these are all hygiene tested prior to use, the process of machining can leave the screws more susceptible to magnetisation over longer time periods. On older sensors this is likely due to exposure to the earth’s field over long periods of time rather than exposure to anything in particular.

What data file format should I choose to download?

There are three options available: Spreadsheet Format, Z string, XYZ Format. In the Spreadsheet format, the data will appear as the layout of the grid, each traverse corresponding to a row of data. The XYZ format will provide the X and Y grid coordinates with the Z value the gradient measured. The Z string corresponds to one column of data where it have been re-arranged, so that it represents the results as would be seen if the data had been collected by a single sensor working in a parallel traverse mode. Note: If Geoplot, by Geoscan Research, is being used to view and process the data then it should be downloaded in Z string format. Import into Geoplot should be done as if the system used was a single sensor gradiometer with survey done in parallel.

Where can I find the Material Safety Datasheet for the BC601 battery?

If I leave my Spectramag-6 unused for a long period of time will the battery be ok?

No it will run flat and will potentially need replacing.

Is it possible to export the raw data from Spectramag-6 for use in other software?

It is possible to export the data from the software in text format, so you can then use it in other programs. There are two ways this can be done, for an existing file .sm6 file, open the file in Spectramag-6, in the file menu there is an export option which will export the data as a text file. If you wish to export the files automatically on acquisition in multiple acquisition mode, in the configuration window, under the general tab you can input a file location and select the tick box to Export ASCII format, then as each run is completed a text file will be sent to the file location entered. This mode only works in multiple mode. In single or continuous you have to revert to the first method.

Can the time series data be ‘cut’ so that only a selected time range can be fed into the FFT?

No this feature is not supported by the software at present. Exporting the data into a text file will allow you to do the necessary cut, but data will need to be processed in an external software.

When acquisition runs in average mode, on export only the time series data from the last run is output, can I access all the data?

The ‘number of averages’ feature takes multiple acquisitions and then outputs the average result in the frequency domain, the time domain will be that of the last scan. It is not possible to separate the averages out using this mode. If you wish to separate the individual acquisitions then the multiple mode should be used, in this mode each acquisition is saved individually. If you then require an average of all the runs then this can be done by combining the data in post processing.

I’m having difficulty connecting the Spectramag-6 to my computer, can you offer any advice?

The following are tips to use when connecting a Spectramag-6 to a computer: Whenever you are installing the software the Spectramag-6 should be disconnected. It may ask you to connect it during driver installation, otherwise it should be connected afterwards. The Spectramag-6 should be plugged in and turned on before opening the software otherwise it may not be detected. If at any point it is unplugged then the software may need to be restarted. If the Spectramag-6 is plugged in before the computer is turned on it is worth disconnecting/reconnecting it before opening the software. If you don’t see it listed when you first open the software, close it, check all connections and reopen the software. If this fails, plug/unplug the Spectramag-6 and wait a few minutes before opening the software.

One other possibility is to ensure that you are administrator on the computer, as well as that the USB connectors are not blocked from communication on the particular machine used for security reasons.

What is the precision of my sensor when used in combination with Spectramag-6?

The Spectramag-6 has a 24 bit Analogue to Digital converter. When used with a Mag-03MCL70, for example, this corresponds to a possible resolution of 8.3pT(140uT/2^24). However, you will also be limited by the noise of the sensor (<6pTrms/√Hz at 1Hz) and the environment it is being used in.

-The data appear to be very drifting from the onset of the acquisition.

Apparent drift can appear in both DC and AC coupling mode if between the previous acquisition and the current acquisition the sensor is being moved from one position to another without having gone through the settling stage. To force the settling, the configuration window need to be opened and closed (even if no changes takes place).

Please can you explain how the gain function works and why it may be useful as this is not obvious?

The gain is applied to the analogue signal prior to digitization. If for example you had an AC signal of within +/- 0.1V but where digitizing the full 10V range you would be digitizing a lot of empty signal and not maximizing the use of the digital sampling. If you applied a gain of 10 prior to digitization you would have an AC signal of +/- 1V prior to digitization, if a gain of 100 you would have an AC signal of +/- 10V prior to digitization and would therefore make better use of your digitizing range. Although the gain is applied to the analogue signal before digitizing this is compensated for so you would still see the correct range on output, it’s just that your signal would be better resolved.

Is it possible to power the Spectramag-6 unit directly from the mains?

By default, the Spectramag-6 is powered by the battery inside the unit, when connected to mains electricity it is still being powered by the battery, the mains is just re-charging it. A modification can be applied to the Spectramag-6 for use directly from the mains. Once this is done however it is no longer possible to plug in the internal battery. As a workaround for this we can provide a modified BC601 battery cassette which can be used as an alternative external power source for the Spectramag-6. This means that the unit can either be powered directly from the mains or from the external battery cassette.

We’re having trouble running the software on some of our computers. All of our computers are Windows 10 and I’d rather not install Windows 7. The unit shows up in Device Manager as “Bartington Input Device” with no yellow sign, but when I try to acquire I always get the error “A problem has occurred and the application needs to be shut down. A diagnostic file has been created”. The diagnostic file contains a bunch of symbols and some ascii text when I open it.

On the computer where the problem exists, could you rerun the installer and running it as administrator (right click on the installer should offer you the option to run as administrator.If that fails you should follow the steps below:

It looks like the installer is failing to install the C++ runtime (2005 and 2010), our software person suspects it is the 2005 that is failing for an unknown reason.It would be helpful if he could remotely connect to one of the affected PCs, but first, you will need to manually run two specific installers (2005 and 2010), these are contained within the installer and not normally visible to the users.

What format is the PSU1/Magmeter-2 output?

The X, Y and Z axes reading are available as single-ended analogue output in the 3 BNC connectors available on the back of the unit. If the sensor is a differential output, the signal will be converted into a single-ended output.

The PSU1/Magmeter-2 is emitting a buzzing noise

This is characteristic of the battery running low. The unit should be connected to the mains for recharging the batteries.

Can the PSU1/Magmeter-2 be operated without batteries, running from mains?

Yes, recent models of both units can run without the batteries installed inside.

Is it recommended to run the PSU1/Magmeter-2 from mains when the batteries are inserted?

Both units can run from mains with the batteries inside the unit without detrimental effect on the signal. For extremely low field measurements, a small amount of noise pick-up is possible and it is therefore recommended to run the units from batteries for this type of measurements.

I am not achieving the full sensor range but the sensor is saturated.

The PSU1/Magmeter-2 deliver a voltage of +/-12V. Some of Bartington Instruments sensor range require +/-15V (such as Mag639). If you are using a sensor needing +/-15V with the PSu1/Magmeter-2, the sensor will operate but will not be able to reach the advertised full range, and will instead display a clipped range (usually up to 10% range reduction). The values between the clipped range will remain linear.

I am only observing negative readings despite turning the sensor in all positions.

Ensure that the front panel setting for balanced/unbalanced is appropriately set for the sensor used (refer to the sensor datasheet for the output mode balanced = differential, unbalanced = single-ended).

I am not measuring DC field or am seeing DC whilst you did not expect to see it?

Check that the AC/DC coupling button on the front panel is set to the correct setting. If it is and the problem persist, press the AC/DC button a few times. If after this the problem does not resolve, return to Bartington for inspection and repairs – contact service@bartington.com.

Noise is visible on the signal once digitised when using the SCU1.

Check the following:

What frequency is the LPF set at? Is it set so as to remove the sensor’s breakthrough?

Is the sampling frequency set to at least 2x the breakthrough frequency of the sensor?

What impedance and length are the BNC cables used between the SCU1 and the A/D card – too long cables which are not shielded can lead to noise being picked up. They should also have a suitable impedance (value to be checked but I think 50 Ohms is ok).

The field displayed on the SCU1 is not what I expect.

Check the following as each will affect the field being displayed on the 3 LCD displays.

Filters, especially the High pass filter (as this could remove the DC component)

Gain

Offset controls (the central position of these is marked by a point (both coarse and fine control) which will be aligned with the reference mark on the SCU1

The displays are in volts rather than µT

Ensure that the balanced/unbalanced switch at the back of the unit is correctly set for the type of sensor being used. Differential sensors should be set to balanced and single-ended sensors to unbalanced

The vertical and/or horizontal degree scales are not centered in their respective windows

Check that the light opening is open and that the mirror is directing light inside the theodolite. If ok, check that the theodolite is properly levelled. If it is, then let the instrument settle for a minute after having moved it. If after that the values are still not centered, then the circle(s) may have been knocked off their axes. The instrument would need to be returned for inspection and repairs. Please inquire to service@bartington.com.

The knobs start to be very tight to turn or the theodolite or telescope to do turn freely

The system may be lacking lubrication. Servicing of the Theodolite is recommended. Enquiry about servicing by contacting service@bartington.com

There is apparent moisture or mould (spots) appearing on the circle

Moisture ingress is difficult to avoid. However the unit should not be stored in a sealed box with moisture inside as this will promote appearance of mould (black spots) on the circles which can over time mask the readings. If mould growth is too important, return of the unit for servicing. Contact service@bartington.com.